DLI (Defense Language Institute) offers some 4,000 GLOSS (Global Language Online Support System) self contained modules in 30 languages ranging from beginner to advanced levels.Here is an in-depth review of FSI courses, presented by renownded polyglot and Linguistics professor Professor Alexander Arguelles. Here, Nelson, also known as “FinnishPractice”, explains the Book2 method and shows some examples. Although the books are available for a small fee, you do not need them to use this course.Here, Paul Jorgensen, a foreign language teacher and student, reviews the strenghts and weaknesses of Duolingo.Here, GLOSS gives a an explanation of the program in under 1 minute.